Cognizant Technology Solutions — confirmation letter yet not received

I attended an interview at CTS Vadodara, Gujarat on 18th of May 2019 and cleared all the rounds and ended up with HR discussion round on same day. At the end HR said to sign on a reallocation norm and informed me that I will receive my offer letter within 10-15 days but I haven't received yet. I am not sure if normally what time they would take to release the offer letter. Please let me know, when can I expect my offer letter.